Nitrided steel articles



Patented Nov. 7, 1933 UNITED STATES PATENT OFFICE NITRIDED STEEL ARTICLES No Drawing. Application May 24, 1929, Serial No. 365,789, and in Germany May 25, 1928 3 Claims. (Cl. 148-31) The invention relates to nitrided steel articles which require high resistance to stresses occurring under high pressure or caused by shocks, such as drawing dies, toothed wheels, claw cou- 5 plings, ball and roller bearings.

With articles of this type which are made of the nitrided steels heretofore used, the drawback appeared that their nitrided layer in the course of time would no longer resist stresses caused by high pressure (more than '10 kg. m?) or by shocks, despite the very great surface hardness. The invention has for its object to afford nitrided articles which are free of this drawback. This object is obtained according to the invention by 5 the fact that the articles are made of an alloyed nitridable steel which after being hardened, by a heat treatment and-then reheated (temper drawn) to at least 450 C. shows a core hardness of about 350 and more according to the Brinell scale.

Steel alloys of about the following composition have proved to be particularly well suited for the manufacture of the indicated articles:

(1) C204 to 0.5%

Si:0.25 to 0.35%

Mn:0.5 to 0.6% Cr:1.2 to 1.5% Mo:0.3% V:0.5% Fe: the remainder and Cr:12% W:08% Fe: the remainder.

The steel as indicated under (1) appertains to the class of oiland water-hardeners, whilst the steel indicated under (2) is to be ranked among 49 the air hardeners. The steel alloys indicated under (1) and (2) can be replaced by steel alloys of other composition which can be nitrided and possess in the core a Brinell hardness of about 350 and more, after having been tempered or drawn by reheating to at least 450 degrees C. The feature that the steel alloys here proposed after the nitriding withstand even in the course of time very high pressure and shock stresses and are not worn thereby, is' due to the fact that with these steel alloys the very hard nitrided layer cannot be forced down into the material of the core when subjected to these high stresses, due to the hardness and toughness of the core.

I claim:-

1. Articles hardened in their surface portions by nitriding and consisting of a steel alloy containing about:

Fe: remainder 2. Articles which in their normal use are subjected to heavy shocks or pressures of over kg. per square millimeter said articles being composed of a steel alloy having approximately the following composition:

Fe: remainder said articles being hardened on their surface portions by nitriding and being further characterized by a core hardness of at least 350 Brinell.

3. Articles which in their normal use are subjected to high pressures or shocks in at least a part of the articles; said articles being composed, at least in those parts which are subjected to such high pressures or shocks, of a nitridable steel alloy consisting of about 2% of carbon, about 12% of chromium, about 0.8% of tungsten, and the remainder principally iron, said steel alloy having a core hardness of at least 350 Brinell, even after being subjected to a temperature of at least 450 C., and at least the parts of said article which are subjected to high pressures or shocks having a surfacehardened by nitriding.

EDOUARD HOUDREMONT.

CERTIFICATE or CORRECTION.

iatent No. 1,934,672. 7 November 7, 1933.

EDOUARD HOUDREMONT,

it is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Line 79, claim 2. for

"C :I%" read C :2%; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

vSign d and sealed this l9th da y otDecember, A. D. 1933.

. Richard $pencer (Seal) Acting Commissioner of Patenta. 

